1. Field of the Invention
The present invention generally relates to tablet coatings. More particularly, the invention relates to a coating useful in masking the odor of pharmaceutical preparations, particularly extracts from the plant Valerian.
2. Description of the Related Art
Pharmaceutical preparations are sometimes associated with unpleasant odors. For example, the strong, unique, unpleasant, and characteristic odor of extracts of the root of the plant Valeriana officinalis L. are well known.
Methods are known for masking such odors. For example, and most typically, flavoring agents may be added to a medicaments (e.g., a pharmaceutical or other formulation) to change the taste of oral medications. Alternative methods to change the smell or taste of medicaments are available, such as smell masking or taste masking. One of the common goals of these various methods of taste and smell masking is to make the medication more appealing to consumers. This goal may lead to an increase in consumer compliance with prescribed and/or recommended dosing regimens.
Extracts of the root of the plant Valeriana officinalis L. (V. officinalis L.) have been used for medicinal purposes for over a century. Certain valerian extracts, including aqueous extracts, are known to have sedative and anxiolytic effects, but the active components have not been clearly and positively identified. See Leathwood P. D., and Behavior, 17:65-71 (1982); Leathwood P. D. and Chauffard F., xe2x80x9cAqueous extract of valerian reduces latency to fall asleep in man,xe2x80x9d Planta Medica, 2:144-148 (1985). Such effects are described by Balandrin et al. in U.S. Pat. No. 5,506,268, which is incorporated by reference herein in its entirety. Presently, valerian is available as dietary supplements; these dietary supplements primarily comprise dried root or extracts from the root, formulated into tablets or gelatin capsules. Each dose contains between approximately 50 mg and approximately 1 gram of dried root or extract.
It is not known in the art which constituents of Valeriana officinalis L., and/or of the other heretofore unidentified members of the Valerianaceae family, are responsible for the sedative and/or anxiolytic action of valerian extracts. Nonetheless, the valepotriates (iridoids) as well as valerenic acid, a sesquiterpenoid compound, and the derivatives of valerenic acid (for example, acetoxyvalerenic acid and hydroxyvalerenic acid) along with the kessane derivatives, valeranone, valerenal, and certain amino acids are present in valerian extracts. Of these components, the valepotriates and valerenic acids are generally considered to contribute to the sedative action of valerian extracts, but have not been clearly and positively identified as such. See Hendriks H. et al., xe2x80x9cPharmacological Screening of valerenal and some other components of essential oil of Valeriana officinalis,xe2x80x9d Planta Medica, 42, 62-68 (1981); Bos R. et al., xe2x80x9cAnalytical aspects of phytotherapeutic valerianxe2x80x9d (1996); Houghton P. J., Valerian. The Genus Valeriana. Harwood Academic Publishers, London. (1997).
The therapeutic benefits of extracts of the root of the plant Valeriana officinalis L. are well-known, and are described in the literature. Such extracts do have a strong, identifying, characteristic and unpleasant smell or odor and an associated disagreeable taste. This characteristic odor and/or this characteristic taste make consuming sufficient therapeutic quantities of the extracts of the root of the plant Valeriana officinalis L. difficult for a substantial percentage of the population. In one reported effort to mask the smell of an extract of the root of a plant of the genus Valeriana, see U.S. Pat. No. 5,211,948 to Cerise et al., the degradation products of valepotriates are identified as the odor causing agents in the aqueous extraction of Valerian root. This reference describes that the odors may be eliminated by, for example, the steps of concentrating the aqueous extract and precipitating the resultant extract with acetone. The precipitated components may then be removed from the rest of the extract via centrifugation. The reference describes that the valerenic acids found in the roots remain present in the resulting extract, and that the resulting extract has a neutral taste and smell. However, as also described in U.S. patent application Ser. No. 60/173,983, entitled xe2x80x9cProcess For Reducing The Odor Of Valeriana,xe2x80x9d and filed on this date and herewith, the disclosure of which is hereby incorporated by reference herein, (1) when an aqueous extract of Valerian root was produced according to a method of the ""948 patent, it was observed that the extract still contained the significant, distinctive, characteristic and pungent smell and associated taste of Valeriana, (2) inconsistent with the teachings of U.S. Pat. No. 5,211,948 to Cerise et al., the characteristic odor of V. officinalis extract may be significantly reduced via the addition of a sufficient amount of a chemical base to the extract formulation, and (3) the addition of base reduces the pungent smell by lowering the vapor pressure of isovaleric acids, and other like acidic components of a V. officinalis extract, which are therefore the source of the characteristic odor and taste.
Certain conventional approaches for masking odors of medicinal preparations, especially tablets, also utilize sugar-coating technology. Such conventional technology typically requires the use of a non-perforated coating pan and generally requires extensive materials, long processing times, multiple stages/layers, and experienced scientists to obtain products with acceptable quality, i.e. odor masking and smooth appearance. Sugar-coating technology has been applied to the commercially available valerian tablet product, Sedonium(copyright), manufactured by Lichtwer Pharma AG, Berlin, Germany. In this product, the weight of the sugar coat applied to each tablet is nearly a half of the core tablet weight.
In the pharmaceutical industry, an alternative coating technique, applicable to tablets, film coating, is generally performed in a perforated coating pan or fluid-bed particle coater. The benefits of film coating, with respect to sugar coating, include: (1) shortened processing time; (2) substantially reduced coating material quantity; (3) easily controlled processing conditions; (4) improved reproducibility from small scale to large scale; and (5) increased selection options for coating materials or polymers.
There is a need in the art for an alternative coating capable of masking odors of various pharmaceutical preparations. The present invention addresses this need, among others.
A pharmaceutically-inert coating is described that is effective in masking the characteristic, unpleasant odor (and/or taste) of a plant or plant extract, and particularly of the root or an extract of the root of the plant Valerian. The coating comprises one or more of the following coating compartments: a first coating compartment comprising a hydroxyalkyl cellulose and an anti-tackiness agent and, optionally, a plasticizer; a second coating compartment comprising a sugar and at least one anti-tackiness agent; and a third coating compartment comprising a methacrylate copolymer, a hydroxyalkyl cellulose and an anti-tackiness agent. The hydroxyalkyl cellulose of the first coating compartment is preferably selected from the group consisting of hydroxyethyl cellulose and hydroxypropyl cellulose. The anti-tackiness agent of the first coating being preferably selected from the group consisting of talc, silicon dioxide, silica hydrogel, microcrystalline cellulose, alkali stearates, and starch. The second coating compartment preferably also comprises a plasticizer; the plasticizer being preferably selected from the group consisting of propylene glycol, glycerin, trimethylolpropane, polyethylene glycols, dibutyl sebacate, acetylated monoglycerides, diethylphthalate, triacetin, glyceryl triacetate, acetyltriethyl citrate and triethyl citrate. The third coating compartment may also comprise a plasticizer; the plasticizer being preferably selected from the group consisting of propylene glycol, glycerin, trimethylolpropane, polyethylene glycols, dibutyl sebacate, acetylated monoglycerides, diethylphthalate, triacetin, glyceryl triacetate, acetyltriethyl citrate and triethyl citrate; and the third compartment may also comprise a water soluble polymer, preferably being selected from the group consisting of hydroxypropyl cellulose, hydroxypropyl methylcellulose, acacia, sodium carboxymethylcellulose, dextrin, alginic acid, ethylcellulose resin, gelatin, guar gum, liquid glucose, methylcellulose, pregelatinized starch, sodium alginate, starch, zein, polyvinylpyrrolindone, vinylpyrrolidone-vinyl acetate copolymer, vinyl acetate-crotonic acid copolymer and ethyl acrylate-methacrylic acid copolymer.